Thanks I've tried that but when I open the query it gives me an error saying "Type mismatch for field..."
This happens when I use 'select (name & lastname)as fullname from...', the query returns that field(fullname) as a TMemofield and then it is impossible to change it to TStringField.

there are two ways of avoiding this, the first one is to make a CAST in SQL to return the field to the type you want : CAST is an SQL Server function, check if it's available in your database.

the second way : remove all fields from field editor and re-add all fields -> delphi gets all the fields with the correct types. if you still have a (MEMO) in your grid, it comes from the fact that the type of that field is not meant to be displayed in a DBGrid : TMemoField has line breaks so it's not meant to be displayed in the cell of a DBGrid. use TDBMemo instead or change the type of your field in your database.